Characterizations of Biomasses for Subsequent Thermochemical Conversion: A Comparative Study of Pine Sawdust and Acacia Tortilis

Abstract

The bioenergy production potential from biomasses is dependent on their characteristics. This study characterized pine sawdust samples from Zimbabwe and acacia tortilis samples from Botswana using conventional and spectrometry techniques. The ultimate analysis results for pine were 45.76% carbon (C), 5.54% hydrogen (H), 0.039% nitrogen (N), 0% sulphur (S) and 48.66% oxygen (O) and, for acacia, were 41.47% C, 5.15% H, 1.23% N, 0% S and 52.15% O. Due to the low N and S in the biomasses, they promise to provide cleaner energy than fossil-based sources. Proximate analysis results, on a dry basis, for acacia were 3.90% ash, 15.59% fixed carbon and 76.51% volatiles matter and 0.83%, 20% and 79.16%, respectively, for pine. A calorific value of 17.57 MJ/kg was obtained for pine, compared with 17.27 MJ/kg for acacia, suggesting they are good thermochemical feedstocks. Acacia’s bulk energy density is five times that of pine, making it excellent for compressed wood applications. Though the ash content in acacia was much higher than in pine, it fell below the fouling and slagging limit of 6%. In pyrolysis, however, high ash contents lead to reduced yields or the quality of bio-oil through catalytic reactions. Fourier transform infrared spectrometry indicated the presence of multiple functional groups, as expected for a biomass and its derivatives.